This invention relates generally to a field core shell typically part of a field core assembly used on an electromagnetic clutch of the type found in automotive air conditioning systems to drive a compressor, and more particularly, to a one-piece field core shell and method of shaping the one-piece field core shell by spin-roll forming.
A typical electromagnetic clutch contains an annular electromagnet coil that fits into a wire winding pod section in the field core shell of a field core assembly.
Field core shells have traditionally been manufactured using a two-piece construction. As shown in FIGS. 1A-C, a press formed top angled piece is attached to a press formed annular bottom piece that contains inner and outer rings used to hold the wire windings of the electromagnetic coil. As illustrated in U.S. Pat. No. 5,273,385, incorporated by reference, an integral blind tubular rivet is used to hold the top angled piece to the bottom piece, forming the completed assembly. This assembly is illustrated in cross-section in FIG. 1C.
Forming a field core shell from a two-piece construction described above and as shown in FIG. 1C is a time consuming and costly process. The cost of manufacturing two separate components that comprise the shell and the cost of assembling those components, may be reduced by forming a one-piece shell.
References in the automotive art that disclose spin-roll forming products from a single piece of metal include U.S. Pat. No. 4,388,817, U.S. Pat. No. 4,532,786, and U.S. Pat. No. 4,936,129. Each of these patents discloses a method of forming an automotive wheel from a single piece of metal wherein, during the wheel-forming process, a peripheral portion of the metal preform is split radially to form two annular split portions, which are then formed into different portions of the wheel rim.
The present invention relates to manufacturing a one-piece field core shell by using spin-roll forming methods. A one-piece field core shell that may be used in a field core assembly such as those found on an electromagnetic clutch of the type found in automotive air conditioning systems.
In accordance with one aspect, the present invention provides for a field core shell made from a single piece of metal typically, a solid circular disk, by a spin-roll forming process. The spin-roll forming process displaces metal from a flat portion (e.g., a flat plate of metal sheet) in a radial and axial direction to produce the one-piece field core shell.
In accordance with another aspect, the present invention provides a spin-roll formed one-piece field core shell that is formed from a disc having top and bottom external surfaces. The core shell has an outer annular ring integral to and encircling a center axis of the disc and extending from the bottom external surface in a direction that is perpendicular to the bottom surface of the disc and parallel to the center axis of the disc. The core shell has an inner annular ring integral to and encircling a center axis of the disc, with the inner annular axis spaced radially inward from the outer annular ring and extending from the bottom external surface in a direction that is perpendicular to the bottom surface of the disc and parallel to the center axis of the disc. The core shell also has a mounting flange integral to the disc, with having a bore extending from the mounting flange to the bottom external surface of the disc.
In accordance with yet another aspect, the present invention provides a method of forming the one-piece field core shell. In the method, a shaping roller is pressed against a side of a spinning annular disc of sheet metal. The shaping roller is moved progressively radially inwardly against the side of the rotating disc which displaces a portion of metal in the form of an axially extending annular wave. The so displaced metal is pressed by an axially moving shaping roller against different mandrels to form a mounting flange and two annular rings opposite the mounting flange to complete the integral one-piece component.
A feature of the invention is to provide a field core shell that is made from a one-piece construction that is less costly and time consuming to manufacture than the current construction.